The present invention relates to a device for connecting the protective plates on bellows covering the guides of automatic machines, machine tools and robots.
Conventional protective bellows usually comprise a folding cover made by suitably folding a flexible material, such as a synthetic fabric, for example. The folding cover is sealed or glued at its transversal folds to a frame inside the bellows. The frame consists of a plurality of ribs or braces made of a relatively rigid material. The ribs are designed to strengthen the folding cover and to give it the required shape inside and outside, according to the type of guide to be protected.
The bellows is fitted over the guide of the automatic machine, machine tool or robot and joined at one end by a connecting flange to a slide that runs in the guide. With its folding cover, the bellows thus covers and protects the guide. As the slide runs backwards and forwards in the guide, the bellows connected to it at one end is compressed and extended in the corresponding direction of motion.
In all automatic machines, especially machine tools and similar types of machinery, where sharp or hot chippings, abrasive powders and corrosive liquids are always present, it is essential to protect the outside surface of the folding cover with protective plates. These plates, which may be made of plastic or metal, are usually connected to the folding cover at the edges of the strengthening ribs by means of joining elements. The joining elements must not only ensure that the plates remain firmly connected to the bellows but must also allow the plates to turn freely relative to the bellows.
The present specification refers to bellows extending in a substantially horizontal direction but without thereby restricting the scope of the invention.
One of the easiest ways of connecting the plates to the bellows is to use U-shaped metal clips. Each clip is applied and fastened to the respective plate with one leg inserted in an aperture made in the edge of the plate and the other leg hooked over the upper edge of the respective strengthening rib. Each clip thus constitutes a sort of hinge for the corresponding plate.
When the slide moves forward, dragging the bellows along with it in such a way as to extend it, the protective plates are positioned in series, one after the other, and lie in a substantially horizontal plane parallel to the upper surface of the folding cover. The plates are partially overlapped in such a way that they can slide over one another. During the return travel of the slide, corresponding to the shortening or compression of the bellows, the plates, in addition to sliding over each other, must be able to turn by approximately 90 degrees in such a way as to be positioned one on top of the other so that they are perpendicular to the upper surface of the folding cover when the bellows is in the position of maximum compression.
The clip is simple in structure and effective in fastening the protective plate to the bellows and allowing the plate to turn relative to the bellows. However, when the bellows moves from the compressed position to the extended position, the clip does not facilitate the return movement of the plate from the turned position where it is substantially perpendicular to the upper surface of the folding cover to the horizontal position where it is parallel to the upper surface of the folding cover. Moreover, substituting a damaged or broken plate requires considerable time and effort.
To overcome the drawbacks mentioned above, several solutions have been proposed. Two of these are described below.
German patent No.3 635 874 teaches the use, as a connecting device, of a hinge that comprises a central portion and two lateral portions on each side of the central portion. Both the central portion and the lateral portions have tubular bodies crossed by a single connecting pin which allows the lateral portions to turn freely relative to the central portion.
The central portion has two legs extending from its tubular body and is designed to be fixed to the bellows with a leg on each side of one of the transversal folds of the bellows.
Each of the two lateral portions also has two legs extending from its tubular body and designed to be fixed to one of the plates with a leg on each side of the plate itself.
The plates are held in contact with each other by return springs located between the central portion and the lateral portions of each hinge.
Hinges made in this way, however, are complex, heavy and expensive and do not greatly facilitate the task of changing the plates.
U.S. Pat. No. 4,596,162 discloses a connecting device consisting of a tape that is substantially the same in length as the protective plate. One longitudinal edge of the tape is fixed to a wall of the bellows and the other longitudinal edge is fixed to the plate. The tape is made of a flexible material and its central longitudinal portion remains slack to allow the plate to turn relative to the bellows.
This solution, too, is difficult to implement and does not solve the problem of enabling a damaged plate to be changed easily.
The aim of the present invention is to provide a device for connecting the protective plates of a covering bellows that is free of the above mentioned drawbacks.
Accordingly, the present invention provides a device for connecting the protective plates of a bellows that covers the guide of an automatic machine, machine tool or robot; the bellows being designed to be extended and compressed longitudinally in a defined direction around a plurality of transversal fold lines; the protective plates being designed to be rotatably joined, each by at least one such connecting device, to the transversal fold lines in such a way as to partially overlap each other in series in a plane that is substantially parallel to a face of the bellows when the bellows is in the extended position and so as to be able to slide and turn relative to each other as the bellows is extended and compressed; the connecting device comprising: a joining element which can be stably connected to the bellows at a respective transversal fold line and which is designed to come into contact with at least one face of the plate; at least one pushing element designed to come into contact with at least one face of the plate; and elastic means located between the joining element and the pushing element.